1. Field of the Invention
The present invention relates to a ratchet type ring spanner having a larger cavity for receiving a larger pawl.
2. Description of the Related Art
Ring spanners can be used in a limited space, e.g., an engine room of a vehicle, as they have a small-size head when compared with other kinds of wrenches. Ratchet type ring spanners have been developed to overcome the problem of insufficient torque-bearing capacity, which largely depends on the size of the pawl. FIGS. 8A and 8B of the drawings illustrate formation of a conventional ratchet type ring spanner by means of placing a T-shaped milling cutter 6 in a hole 2 in the head 9 and then moving the T-shaped milling cutter 6 toward the handle 1, thereby forming a cavity 3 in a web between the head 9 and the handle 1. However, the size of the cavity 3 thus formed is limited, as the shaft 7 of the T-shaped cutter 6 is restrained by an inner periphery defining the hole 2 of the head 9. Namely, the cavity 3 is relatively shallow and thus only capable of receiving a pawl 4 having a relatively small thickness. As a result, the pawl 4 that engages with a drive wheel 5 (FIG. 9) rotatably received in the hole 2 of the head 9 for driving fasteners cannot provide a high torque-bearing capacity.
In addition, as illustrated in FIG. 9, the pawl 4 is pressed against a wall defining the cavity 3 at a point 8 that is relatively away from a center of the wall defining the cavity 3. Typically, the pressing point 8 approximately corresponds to the position of the third tooth of the pawl 4 counting from an adjacent end of the pawl 4. There is no support for the inner lateral side of the pawl 4 facing away from the gear wheel 5. Thus, no reactive force is obtained when the pawl 4 is subjected to a force greater than a critical value. The other lateral side of the pawl 4 facing the gear wheel 5 pivots about the pressing point 8 and slightly disengages from the teeth of the gear wheel 4. As a result, a seesaw effect is incurred on the pawl 4 which leads to a poor engagement between the pawl 4 and the gear wheel 5; namely, the pawl 4 merely engages with the gear wheel 5 by the first three teeth, which tends to cause damage to these three teeth. A solution to increase the torque-bearing capacity is to increase the size of the pawl 4, yet this contradicts the advantage of ring spanners for use in limited spaces, as the size of the head 9 is also increased.
An object of the present invention is to provide a ratchet type ring spanner having a larger cavity for receiving a larger pawl.
A ratchet type ring spanner comprises a handle having a larger cavity for receiving a larger pawl to thereby provide an improved torque-bearing capacity. The pawl is configured to be pressed against a wall defining the cavity of the handle in a manner that the torque is exerted on all of the teeth of the pawl in a more balanced manner to further improve the torque-bearing capacity.
In accordance with a preferred embodiment of the invention, a ratchet type ring spanner comprises:
a handle having a cavity, the handle further comprising two lateral sides, a transverse hole being defined in each said lateral side and communicated with the cavity, a first switch rod and a second switch rod being respectively, slidably mounted in the transverse holes, each of the first switch rod and the second switch rod having an outer end and an inner end, the first switch rod and the second switch rod being movable between a first position corresponding to a first ratcheting direction of the ratchet type ring spanner and a second position corresponding to a second ratcheting direction opposite to the first ratcheting direction;
a head extending from the handle and comprising a hole communicated with the cavity of the handle;
a drive member rotatably mounted in the hole of the head, the drive member comprising a plurality of teeth on an outer periphery thereof;
a pawl slidably mounted in the cavity of the handle, the pawl comprising a first lateral side facing the drive member and a second lateral side facing away from the drive member, the first lateral side of the pawl having a plurality of teeth for meshing with the plurality of teeth of the drive member, the second lateral side of the pawl comprising a first positioning section and a second positioning section, the pawl further comprising a first end adjacent to the first positioning section and a first arcuate face between the first end and the first positioning section, the pawl further comprising a second end adjacent to the second positioning section and a second arcuate face between the second end and the second positioning section; and
means for selectively engaging with one of the first positioning section and the second positioning section of the pawl to bias the pawl to engage with the plurality of teeth of the drive member corresponding to the position of the first switch rod and the second switch rod;
wherein when the first switch rod and the second switch rod are in the first position, the first end of the pawl is pressed against the inner end of the first switch rod, the second end of the pawl is pressed against and in face-to-face contact with the inner end of the second switch rod, and the second arcuate face of the pawl is pressed against and in face-to-face contact with a wall defining the cavity of the handle; and
wherein when the first switch rod and the second switch rod are in the second position, the second end of the pawl is pressed against the inner end of the second switch rod, the first end of the pawl is pressed against and in face-to-face contact with the inner end of the first switch rod, and the first arcuate face of the pawl is pressed against and in face-to-face contact with the wall defining the cavity of the handle.
Other objects, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.